Electrostatic chucking device

ABSTRACT

The present invention is to provide an electrostatic chucking device having improved heat conductivity and at the same time increased adsorption area and improved adsorptity as well as having no uneveness on the wafer-provided face. The electrostatic chucking device of the present invention comprises a metal base, an adhesive layer, an electrode layer comprising a metal-deposited or metal-plated layer, and an electrically insulating layer possessing a face for providing a substance to be adhered by suction, laminated thereon in this order. The electrostatic chucking device is produced by a process comprising a stage for forming a metal-deposited or metal-plated layer on one face of a heat resistant film, a stage for providing a photoresist layer on the surface of the electrode layer, carrying out pattern exposure, development, and an etching processing, a stage for forming a semi-cured adhesive layer on the surface of the etched electrode layer, a stage for punching the formed laminated sheet according to the shape of a metal base, and stage for laminating the metal base and the laminate sheet via the above-mentioned adhesive and curing the laminated product.

This application is a division of application Ser. No. 08/561,731 filedNov. 22, 1995 now U.S. Pat. No. 5,645,921.

BACKGROUND OF THE INVENTION

1) Field of the Invention

This invention relates to an electrostatic chucking device such as adevice for producing an semiconductor integrated circuit which can fixand hold an electrically conductive substance such as a wafer on aprescribed portion of a processor in vacuum, and a process for producingthe same, and particularly to an electrostatic chucking device havingimproved heat conductivity (heat radiation ability or temperatureregulating ability) and improved adhesion by suction.

2) Description of Related Art

In the stage for processing a semiconductor wafer, it is required to fixand hold the semiconductor wafer on a prescribed portion of a processor.In particular, in the manufacture of an integrated circuit in which finepatterns are drawn on the semiconductor wafer to form a lot ofsemiconductor elements, it is necessary to ensure the holding of thesemiconductor wafer on a flat face.

In conventional, as means for holding the semiconductor wafer, achucking device in a mechanical, vacuum (utilizing the differencebetween fluids) or electric manner has been utilized. Of these, thechucking device in an electric manner, i.e., an electrostatic chuckingdevice, has the merits that even in the case of an uneven semiconductorwafer, it can be fixed in a close manner, the device can easily behandled and easily be used even in vacuum, etc.

When beam particles, etc. are injected and impacted during theprocessing of the semiconductor wafer, heat energy is generated on thesemiconductor wafer. In the case where the heat energy cannot easily bedischarged, the local swelling and deformation of the semiconductorwafer will be caused. Consequently, it is necessary that the heatgenerated during the processing is escaped to the side of the metal baseto make temperature distribution on the semiconductor wafer uniform. Forthis reason, it is desired for the electrostatic chucking deviceutilizing in these applications to have functions of holding thesemiconductor wafer on a prescribed portion without failing and at thesame time of having high heat conductivity.

One embodiment of the conventional electrostatic chucking device, forexample, as disclosed in Japanese Patent Publication 87177/93, will bedescribed by referring to the drawing. FIG. 4 is a schematiccross-sectional view showing one embodiment of the conventionalelectrostatic chucking device. A metal base 1 is made up of a highlyheat conductive metal such as copper and aluminium. On the metal base 1,in order to regulate the temperature by passing isothermic water, etc.,spaces 6 for regulating temperature are provided. While an electrodelayer 3a is provided on an upper portion of the metal base 1 so as tohave a function of electric chucking, an insulating plastic film 4b isprovided between the electrode layer and the metal base in order toavoid any electric shortage among the electrode layer, the metal baseand external portions. On the upper portion of the electrode layer 3provided on the insulating plastic film 4b, a plastic film 4a isprovided so as to cause a semiconductor wafer 5 to exhibit adhesion bysuction and to protect the metal base 1.

In the above-mentioned electrostatic chucking device, as the electrodematerial for the electrode layer 3a, a copper foil having a thickness of1/2 oz (approximately 18 microns) or 1 oz (approximately 35 microns) isgenerally used, and as the insulating plastic films 4a and 4b, filmshaving a thickness of approximately 50 microns such as made of polyimideor Teflon are used considering electric characteristics and heatresistance. They are laminated each other via adhesive layers having athickness of from 10 microns to 50 microns (2a, 2b, 2c).

In the conventional electrostatic chucking device, since the plasticfilms 4a and 4b are interposed between the semiconductor wafer 5 and themetal base 1 in order to secure mutual electric insulation between thesemiconductor wafer 5, the electrode layer 3a and the metal base 1, thefunction of regulating temperature is poor due to the low heatconductivity thereof. In other words, there poses a problem that acooling function of the circuit base to the semiconductor wafer isinsufficiently acted.

Since a metal foil having a thickness of approximately from 18 to 35microns is used as the electrode layer, uneveness in approximately thesame degree as thickness of the metal foil used as the electric layeroccurs between the portion where the electrode exists and the portionwhere no electrode is existent on the wafer-provided face (suction face)of the electrostatic chucking device. Consequently, there is a problemthat the heat conductivity in vacuum becomes locally poor when thesemiconductor wafer is fixed by suction, because the semiconductor waferis separated at the cavity portion. This phenomenon is significant atthe outer circumference where no cooling gas is used, and the portion ofthe width of insulation is co-called in a floated state, causing theproblem that the heat conductivity in vacuum becomes poor.

Moreover, an adhesive is used for laminating these materials. However,when being corrugated, since there are large cavities at these bumpportions, which is difficult to be filled up by an adhesive and, thus,fine cavities are formed along the bump, the width of insulation againstthe outer circumference should be widened in relation to dielectricstrength. This causes the problem that the adsorption area becomesnarrow.

FIG. 5 explains the above state in the conventional electrostaticchucking device, and shows the state that the uneveness is formed on thewafer-provided face of the plastic film, spaces 7 are formed whenproviding the semiconductor wafer, and cavities 8 are formed along thebump. The other symbols in FIG. 5 are the same as those described above.

SUMMARY OF THE INVENTION

An object of the present invention is therefore to provide anelectrostatic chucking device having improved heat conductivity and atthe same time increased adsorption area and improved adsorption power aswell as having no uneveness on the wafer-provided face.

Another object of the present invention is to provide a process forproducing the above-mentioned electrostatic chucking device.

The electrostatic chucking device of the present invention ischaracterized by comprising a metal base, an adhesive layer, anelectrode layer comprising a metal-deposited or metal-plated layer, andan electrically insulating layer possessing a face for providing asubstance to be adhered by suction, laminated thereon in this order.

The process for producing the electrostatic chucking device of thepresent invention is characterized by comprising a stage for forming ametal-deposited or metal-plated layer on one face of a heat resistantfilm, a stage for providing a photoresist layer on the surface of theelectrode layer, and carrying out pattern exposure, development and anetching processing, a stage for providing a semi-cured adhesive layer onthe surface of the etched electrode layer, a stage for punching out theformed laminate sheet according to the shape of a metal base, and astage for laminating the metal base and the laminate sheet via theabove-mentioned adhesive and curing the laminated product.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing one embodiment of anelectrostatic chucking device according to the present invention;

FIG. 2 is a graph showing the state of the surface temperature of thesemiconductor wafer in the electrostatic chucking device according toExample 1;

FIG. 3 is a graph showing the state of the surface temperature of thesemiconductor wafer in the electrostatic chucking device according toComparative Example 1;

FIG. 4 is a schematic cross-sectional view showing one embodiment of theconventional electrostatic chucking device; and

FIG. 5 is an explanation view illustrating the state that spaces andcavities are formed in the conventional electrostatic chucking device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will now be described in detail by referring tothe drawings. FIG. 1 is a schematic cross-sectional view showing oneembodiment of an electrostatic chucking device according to the presentinvention. The electrostatic chucking device of the present inventionhas a construction where an adhesive layer 2 is formed on a metal base1, a electrode layer 3 comprising a metal-deposited or metal-platedlayer is provided thereon, and an electrically insulating layer 4comprising a plastic film is provided thereon, the surface of theplastic film making up a face for providing a substance to be adhered bysuction. The electrode layer is provided for the purpose of generating apolarization charge on the face of the electrically insulating layer onwhich a substance to be adsorbed is provided, and is formed by using ametal-deposited or metal-plated layer to form a pattern which meets themetal base. Symbol 5 is a semiconductor wafer and 6 is a space forregulating a temperature.

The metals which is used for deposition or plating, and metal such ascopper, aluminium, tin, nickel, and chromium can be used as long as itcan easily be deposited or plated and can easily be subjected to patternformation by wet-etching, etc., and the material is not specificallyrestricted as long as they provide stable electric conductivity andprocessing ability.

The thickness of the deposited layer or plated layer is in the range offrom 100 angstroms to 10 microns. In the case of a highly reactivematerial such as aluminium, since the workability is poor and at thesame time it is difficult to maintain a stable electric conductivity ifthe layer thickness is not more 200 angstroms, the thickness ispreferably not less than 200 angstroms. The most preferable range of thefilm thickness of the deposited layer or plated layer is from 500angstroms to 5 microns, and the layer thickness in this range is mosteasily used.

The electric insulating layer is a base for forming the electrode layerby the deposition or plating, and an insulating plastic film is used. Inthe present invention, considering electric characteristics such as ε,tan θ, and dielectric strength, a polyimide film having a thickness offrom 20 to 75 microns or a heat-resistant plastic film over 150° C. ispreferably used, with a polyimide film being most preferably used.

Examples of the polyimide films include Kapton, Dupont, Toray Dupont),Apical (KANEKA CORPORATION), Upilex (Ube Industries, Ltd.), and thelike.

Examples of the plastic films having heat resistance over 150° C.include films made of a fluorine resin (e.g., a fluoroethylene-propylenecopolymer), polyether sulfone, polyether ether ketone, cellulosetriacetate, silicone rubber, etc.

The thickness of the electric insulating layer selected is in the rangeof from 20 to 75 microns. Although the thickness is preferable as thinas possible in terms of the function, the thickness of approximately 50microns is preferably selected from the viewpoints of mechanicalstrength, dielectric strength and durability.

The adhesive layer (insulating layer) used for adhering these materialsto the metal base is required to comprise an adhesive having an adhesionforce to the three materials, i.e., the electric insulating layer, theelectrode layer, and the metal base, and having excellent heatresistance. A thermosetting adhesive, a two-liquid ingredient systemcurable adhesive, or a thermoplastic adhesive is used.

Examples of effective adhesives are epoxy, polyimide, modifiedpolyimide, rubber, polyamideimide, polyester type adhesives, and theseadhesives can be used singly or as a mixture of two or more thereof.

Although the heat conductivity of the electric insulating layer andadhesive layer in the electrostatic chucking device of the presentinvention are similar to that of the conventional type because of usingsimilar raw materials, the total thickness of the laminate sheet in thepresent invention may be 1/2 to 1/3 times that of the conventional one,since the plastic film conventionally existing on the side of the metalplate is omitted, since the electrode layer is substituted by a thinmetal-deposited or metal-plated layer, and since the adhesive layercomprises one layer. Consequently, the electrostatic chucking device ofthe present invention have the improvement that the total heatconductivity (heat radiation ability or temperature-regulating ability)is 2 to 3 times better than that of the conventional device.

As a result of providing the thin electrode layer, the bump whichconventionally exists do not exist and, thus, no cavity around outercircumference of the electrode formed due to the existence of the bump.Consequently, it is possible to set the width of the insulation area ofthe outer circumference as narrow as 1/3 times or less of theconventional width and, at the same time, there is no uneveness on thesuction surface, thereby improving the adhesion to the semiconductorwafer and, particularly, achieving the increase and stabilization of theadhesion by suction due to improvement of heat conductivity of the outercircumference of the electrode and increase of the suction area.

The process for producing the electrostatics chucking device of thepresent invention will now be described. First, a metal layer is formedon one face of a heat resistant film by a depositing or plating method,and a photoresist layer is formed on the face of the metal layer. Thephotoresist layer may be formed by applying a liquid resist followed bydrying or laminating a photoresist film (dry film) by a heat press.

Subsequently, pattern exposure, developing, etching, washing, removal orresist, and drying are carried out to form an electrode layer having aprescribed form. These operations may be carried out using a knownmethod for forming a photoresist pattern.

On the metal face of the etched electrode layer, an adhesive is applied,dried to form a semi-cured adhesive layer, thereby producing a laminatesheet. The formed laminate sheet is subjected to punching processingaccording to the shape of the metal base to produce a laminate sheet forthe electrostatic chucking device.

The laminate sheet for the electrostatic chucking device produced asmentioned above is then allowed to adhere to the metal base, followed bycuring the adhesive layer to produce the electrostatic chucking device.

In the process of the present invention, means for providing thesemi-cured adhesive layer on the surface of the electrode include thefollowing means in addition to the above mentioned means of applying theadhesive. An adhesive sheet is previously produced by forming asemi-cured adhesive layer on a surface of a releasing film byapplication of the adhesive and then laminating a protective filmthereon. After punched the laminate sheet and removed the protectivefilm from the adhesive sheet just before application, the adhesive sheetis allowed to adhere to the surface of electrode layer to form alaminate sheet. Using this laminate sheet, the electrostatic chuckingdevice of the present invention can be produced by removing thereleasing film from the laminate sheet and allowing to adhere to themetal base, followed by curing the adhesive layer.

Effect of the Invention

Since the electrostatic chucking device of the present invention isformed by using a simple laminate sheet having a thin thickness, theproblem associated with the use of the conventional polyimide typeelectrostatic chucking device is solved, and the device of the presentinvention exhibits excellent effects that the heat conductivity isimproved, the adsorption area and adsorptity can be improved, and thereis no uneveness on the wafer-provided face.

To be specific, since in the electrostatic chucking device of thepresent invention, the conventionally used polyimide film is used as itis, and a plated or deposited layer as a very thin electrode layer isdirectly formed on one face thereof without interruption with anyadhesive layer, and the total thickness of the laminate sheet isdrastically thinned, which drastically improves the heat conductivity,since it is directly adhered to the metal base by an adhesive.Furthermore, since the electrode layer comprises a very thin depositedor plated layer, the bump due to the electrode is never formed and,thus, the semiconductor-provided face can be flat without forminguneveness and, at the same time, cavities which are generated in theconventional electrostatic chucking device due to the fact that theuneveness cannot be filled up only by the adhesive. As a result, thewidth of the insulation around the outer circumference can become narrowwhich provides the effects that the adsorption area and adsorptity canbe increased.

EXAMPLES

The present invention will be described in greater detail by referringto Example and Comparative Example. The parts used hereinbelow are basedon weight.

Example 1

Onto a 50 micron thick polyimide film (Kapton, produced by Toray Dupont)was deposited aluminum in the thickness of 300 angstroms, a negativetype photosensitive film (OZATEC-T538, produced by Hoechest Japan) waslaminated thereon, and an electrode layer having a prescribed shape wasproduced by procedures of exposure, developing, etching, washing, anddrying. The developing was carried out by using an aqueous 1% sodiumcarbonate solution which was spray-injected, the etching was carried outby using an aqueous solution comprising ferrous chloride, ferricchloride, and hydrochloric acid, which was spray-injected, and thewashing was carried out by using ion-exchanged water.

Subsequently, using an adhesive having the following composition, thefirst application onto the surface of the electrode layer was carriedout and then dried at 150° C. for 5 minutes and the second applicationwas carried out to form an adhesive layer (insulating layer) having afilm thickness of 40 microns.

    ______________________________________                                        Acrylonitrile-butadiene rubber                                                                            100 parts                                         (Nipole 1001, produced by Nippon Zeon Co, Ltd.)                               Highly pure epoxy resin     50 parts                                          (Epikoat YL979, produced by Yuka Shell Epoxy Kabushiki                        Kaisha)                                                                       Cresol type phenol resin    50 parts                                          (CKM 2400, produced by Showa Highpolymer Co., Ltd.)                           Dicyanediamide              5 parts                                           Methyl ethyl ketone         500 parts                                         ______________________________________                                    

The total thickness of the resulting laminate was 90 microns. Thislaminate sheet was subjected to punching processing according to aprescribed size of a aluminum base, laminated to the aluminum base. Astepwise curing from 100° to 150° C. was carried out for 5 hours toproduce an electrostatic chucking device having an electrostaticchucking face with a diameter of 8 inches.

Comparative Example 1

A first adhesive layer was applied on a 50 micron thick polyimide film(Kapton, produced by Toray Dupont) in a thickness of 10 microns usingthe adhesive used in Example 1, dried at 150° C. for 5 minutes, a 23micron thick copper foil was laminated thereon, and the curing wascarried out under the same conditions as in Example 1. A negativephotosensitive film was laminated on the copper foil face of thelaminate sheet, and an electrode in a prescribed shape was produced asin Example 1.

On the other hand, a 10 micron thick second adhesive layer wasseparately applied on another polyimide film (Kapton, 50 microns), thiswas laminated on the pattern electrode face produced as described above,and curing was similarly carried out. This laminate sheet was subjectedto punching processing according to a prescribed size of an aluminumbase, and laminated to the aluminum base using the same adhesive asdescribed above. The total thickness of the resulting laminate sheet was155 microns.

Using the electrostatic chucking devices obtained from Example 1 andComparative Example 1, the surface temperatures of the semiconductorwafer were measured. The results are shown in the follwing Table 1.

A temperature measuring plate was adhered on an Si wafer, the dischargewas carried out under the following etching conditions, the temperaturesof central, middle, and edge portions were measured.

The applied voltage for electrostatic adsorption was 2.0 KV.

(Etching conditions)

High frequency output applied to the electrode for the generation ofplasma=1400 (W); vacuum degree in the chamber=40 (mT); packing gas inthe chamber: CHF₃ /CO=45/155 (sccm); He gas being into contact with theelectrostatic chucking face (Back pressure He)=10 (Torr); temperature inthe chamber (upper portion/side face/bottom portion)=60/60/20 (° C.)

(Result)

                  TABLE 1                                                         ______________________________________                                                       Central    Middle  Edge                                                       portion    portion portion                                     ______________________________________                                        Example 1      71-76      71-76   87-93                                       Comparative Example 1                                                                        71-76      71-76   98-104                                      ______________________________________                                         Note): the unit is °C.                                            

As is clear from Table 1, it was proven that in the thin type productaccording to the present invention, the temperature in the face at theedge portion of the wafer was low indicating that a heat radiationeffect was high.

Similar to the above test, using high frequency output 1200 W and 1600W, the surface temperatures of the semiconductor wafer were measured.These results are shown in FIGS. 2 and 3, together with the results inthe case of the above high frequency output 1400 W.

As is clear comparison between Example 1 (FIG. 2) and ComparativeExample 1 (FIG. 3), it was proven that the electrostatic chucking deviceof the present invention has higher heat radiation effect.

What is claimed is:
 1. A process for producing an electrostatic chuckingdevice comprising:forming a metal layer on one face of a heat resistantfilm using a depositing or plating method; forming an electrode layer byproviding a photoresist layer on the surface of the metal layer, andcarrying out pattern exposure, development, and etching processes;forming a laminated sheet by forming a semi-cured adhesive layer on thesurface of the electrode layer using an adhesive; punching the laminatedsheet according to the shape of a metal base; adhering the punchedlaminated sheet on the metal base by placing the semi-cured adhesivelayer in contact with the metal base; and curing the semi-cured adhesivelayer to form a laminated product.
 2. A process for producing anelectrostatic chucking device according to claim 1, wherein saidsemi-cured adhesive layer is formed by applying the adhesive to thesurface of the electrode layer.
 3. A process for producing anelectrostatic chucking device according to claim 1, wherein saidsemi-cured adhesive layer is formed by forming the adhesive into a sheetof semi-cured adhesive and laminating the sheet on a surface of areleasing film.
 4. A process for producing an electrostatic chuckingdevice according to claim 1, wherein said adhesive exhibits adhesionwith respect to three different materials.
 5. A process for producing anelectrostatic chucking device according to claim 4, wherein said threedifferent materials are respectively included in an electric insulatinglayer, and electrode layer and a metal layer.
 6. A process for producingan electrostatic chucking device according to claim 1, wherein saidadhesive is one of a thermosetting adhesive, a two-liquid ingredientsystem curable adhesive, and a thermoplastic adhesive.